[R] Design matrix labels
j.logsdon at lancaster.ac.uk
Mon Jan 25 23:08:09 CET 1999
If I have two factors A and B with levels '1','2','3' and '1','4','6','8'
recpectively (note the gaps in the second one). As factors, the levels
are named as above while of course the internal codes are (1,2,3) and
I want to make a design matrix of these as one would in a linear model
except I can't use lm or glm since the error distribution is not
tractable. So I generate an overall factor as 10*A+B (for example) then
the internal codes and levels become 11,12,13,14,21,22,23,24,31,32,33,34.
I don't mind the internal codes, but is there a neater way of generating
the lm-type of factor levels a A*B to give the levels
Better still would be to assign proper labels to the levels and get
factors a 'A1.B1','A1.B2' etc., basically mimicking the standard notation.
Is there a proper way to do this other than for-looping and pasting? I
don't really want to create a hand-mapping because it is not robust to
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